Tropical Storm LIONROCK Advisory Sun Aug 28

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (LIONROCK) WARNING NR 43//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 12W (LIONROCK), LOCATED APPROXIMATELY 410 NM SOUTH OF
YOKOSUKA, JAPAN, HAS TRACKED NORTHEASTWARD AT 12 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND
RECENT MICROWAVE IMAGERY DEPICT A COMPACT, STRENGTHENING CORE
(APPROXIMATELY 60-NM DIAMETER EYEWALL) WITH A 28-NM ROUND EYE,
WHICH PROVIDES HIGH CONFIDENCE IN THE CURRENT POSITION AND RECENT
TRACK ACCELERATION TO THE NORTHEAST. ANIMATED WATER VAPOR IMAGERY
CONTINUES TO INDICATE RADIAL OUTFLOW, HOWEVER, THE DEEP UPPER-LEVEL
TROUGH OVER WESTERN JAPAN IS JUST BEGINNING TO IMPINGE ON THE
NORTHWEST PERIPHERY OF THE SYSTEM. RECENT MICROWAVE IMAGERY SUGGESTS
THE ONSET OF AN EYEWALL REPLACEMENT CYCLE (ERC) WITH A SECONDARY
EYEWALL AND MOAT FORMING, HOWEVER, CORE CONVECTION REMAINS VIGOROUS
AND DVORAK INTENSITY ESTIMATES FROM ALL AGENCIES HAVE MAINTAINED AT
T6.0 (115 KNOTS). CONSEQUENTLY, THE CURRENT INTENSITY REMAINS
ASSESSED AT 115 KNOTS ALTHOUGH POTENTIAL ERC AND DECREASING SATCON
ESTIMATES OF 109 KNOTS MAY SIGNAL A WEAKENING TREND. TY 12W IS
CURRENTLY TRACKING ALONG A POLEWARD EXTENSION OF THE NEAR-EQUATORIAL
RIDGE (NER) POSITIONED TO THE EAST. RECENT 500MB ANALYSES DEPICT A
DEEPENING LOW OVER THE KOREAN PENINSULA AND ASSOCIATED MAJOR
SHORTWAVE TROUGH DIGGING INTO THE EAST CHINA SEA AND WESTERN JAPAN.
OVERALL, THE DYNAMIC MODELS HAVE DONE AN EXCELLENT JOB IN
FORECASTING THE DEVELOPMENT OF THIS EXPANSIVE, STRONG LOW AND MAJOR
SHORTWAVE TROUGH, AND ARE CURRENTLY ACCURATELY INITIALIZING THIS
SYNOPIC FEATURE, WHICH WILL BECOME THE DOMINANT INFLUENCE ON TY
12W'S TRACK AND INTENSITY AFTER TAU 12.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE. THE FORECAST TRACK AND CPA TO
YOKOSUKA REMAIN HIGHLY CONSISTENT WITH THE PREVIOUS JTWC FORECAST
TRACK.
   B. TY 12W WILL CONTINUE TO TRACK NORTHEASTWARD ALONG THE
NORTHWEST PERIPHERY OF THE NER THROUGH TAU 24. AFTER TAU 24, THE
AFOREMENTIONED UPPER LOW AND MAJOR SHORTWAVE TROUGH ARE FORECAST TO
REMAIN ENTRENCHED OVER THE EAST SEA AND JAPAN WITH THE PRIMARY
STEERING RIDGE POSITIONED OVER SAKHALIN ISLAND AND THE SEA OF
OKHOTSK, EXTENDING SOUTHEASTWARD ACROSS THE KURIL ISLANDS. TY 12W IS
FORECAST TO RE-CURVE WITHIN THE ENHANCED FLOW BETWEEN THESE TWO
SYNOPTIC FEATURES. FOR THE FIRST TIME ALL CONSENSUS DYNAMIC MODEL
TRACKERS NOW SUPPORT THE RE-CURVE SCENARIO AND SHOW A TRACK OVER
NORTHERN HONSHU THEN A RAPID NORTHWESTWARD TRACK ACROSS THE EAST
SEA. ADDITIONALLY, THE BULK OF THE JGSM AND ECMWF ENSEMBLE MEMBERS
NOW SHOW SOLUTIONS TRACKING OVER NORTHERN HONSHU, WHICH FURTHER
BOLSTERS THE RE-CURVE SCENARIO. DESPITE THE IMPROVED AGREEMENT,
THERE REMAINS SOME UNCERTAINTY IN THE EXACT TRACK EAST OF YOKOSUKA
WITH A 110-NM SPREAD IN SOLUTIONS. ADDITIONALLY, THERE IS A LARGER
DEGREE OF UNCERTAINTY IN THE EXACT RE-CURVE POINT AND TRACK SPEEDS
AFTER TAU 36. THE CURRENT INTENSITY IS ASSESSED AT 115 KNOTS, WHICH,
BASED ON THE ERC SUGGESTED IN MICROWAVE IMAGERY AND IMPINGEMENT OF
POLEWARD FLOW REVEALED IN ANIMATED WATER IMAGERY, MAY BE THE PEAK
INTENSITY. THEREFORE, TY 12W IS FORECAST TO GRADUALLY WEAKEN THROUGH
TAU 24 WITH FURTHER WEAKENING AFTER TAU 24 DUE TO COOLER SST,
INCREASING VWS AND INTERACTION WITH LAND. ADDITIONALLY, TY 12W
SHOULD BEGIN EXTRA-TROPICAL TRANSITION (ETT) JUST AFTER TAU 48, AS
IT BEGINS TO INTERACT WITH THE MAJOR SHORTWAVE TROUGH. AFTER
CROSSING THE MOUNTAINOUS TERRAIN OF NORTHERN HONSHU, A MUCH WEAKER
SYSTEM IS EXPECTED TO RE-EMERGE IN THE EAST SEA AND TO ACCELERATE
NORTHWESTWARD WITHIN THE ENHANCED FLOW BETWEEN THE STRONG BAROCLINIC
LOW AND THE STEERING RIDGE. TY 12W IS FORECAST TO COMPLETE ETT BY
TAU 72 AS IT BECOMES EMBEDDED WITHIN THE BAROCLINIC LOW. DUE TO THE
UNCERTAINTY IN THE RE-CURVE POINT, WHICH IS TIED TO UNCERTAINTY IN
THE DEPTH AND ORIENTATION OF THE STRONG UPPER LOW, THERE IS LOW
CONFIDENCE IN THE FORECAST TRACK.//
NNNN
NNNN